1Field of the Invention
The present invention generally relates to an optical disk apparatus, and more particularly to an optical disk apparatus in which a rotation of a disk motor is controlled to keep a linear velocity of an optical disk constant.
2Description of the Prior Art
There are two types of disk rotation control methods for controlling a rotation of a disk motor on an optical disk device to keep a rotating velocity of an optical disk constant: one is a Constant Angular Velocity (CAV) method and the other is a Constant Linear Velocity (CLV) method. Many compact disk devices in these years use the CLV method to control the rotation of the disk motor.
In a conventional optical disk apparatus which uses the CLV method, the rotation of the disk motor is controlled to always set the linear velocity of the disk at a fixed constant value even though the pickup lies at any position of the disk. As the linear velocity of the disk is kept constant, a rotating speed of the disk motor when the pickup is located at an inner position of the disk and a rotating speed of the disk motor when the pickup is located at an outer position of the disk have to differ from each other. If the pickup is moved towards the center of the disk the magnitude of the rotating speed of the disk motor must increase, and, on the other hand, if the pickup is moved towards the periphery of the disk the magnitude of the rotating speed of the disk motor must decrease.
FIG. 3 shows a conventional optical disk apparatus 51. In this optical disk apparatus, after a seek is performed by a pickup to jump from the present track of a disk to a destination track thereof, a CLV servo control procedure based on a data signal read from the destination track of the disk is carried out.
In the optical disk apparatus 51 in FIG. 3, a disk 22 is irradiated with a laser beam from a pickup 25 so that a data signal is read from the disk 22. The data signal indicates data read from the disk 22. The pickup 25 supplies the data signal to a sync detecting unit 30 and a phase-locked loop (PLL) circuit 31 through a waveform shaping unit 28.
At the PLL circuit 31, a phase of the data signal from the waveform shaping unit 28 is locked to a phase of a reference signal supplied from an oscillator (not shown in FIG. 3) to generate a clock signal used to carry out demodulation. This clock signal from the PLL circuit 31 is supplied to the sync detecting unit 30, a signal processing unit 32, and a disk servo unit 53 at the same time.
The sync detecting unit 30 supplies the data signal, output from the waveform shaping unit 28, to the signal processing unit 32 in synchronism with the clock signal from the PLL circuit 31.
At the signal processing unit 32, error correction and analog-to-digital conversion processes are carried out for the data signal supplied from the sync detecting unit 30. After those processes are carried out, the signal processing unit 32 supplies a processed signal to a track address detecting unit 33. This processed signal may be supplied also to another unit (not shown in FIG. 3) of the optical disk apparatus 51. However, for the sake of convenience, a description thereof will be omitted.
The track address detecting unit 33 detects a track address based on the processed signal supplied from the signal processing unit 32, and outputs a signal indicating the track address information to a central processing unit (CPU) 52.
The CPU 52 generates a control signal based on the track address information from the track address detecting unit 33, and supplies the control signal to the pickup servo unit 35 to control focusing, tracking and 10 feeding operations of the pickup 25 through the pickup servo unit 35.
The pickup servo unit 35 generates a focusing signal, a tracking signal or a feeding signal based on the data signal from the pickup 25 under the control of the CPU 52, and supplies one of these signals to the pickup 25 to control the focusing operation, tracking operation or feeding operation of the pickup 25.
The disk servo unit 53 is connected to a disk motor 23 which rotates the disk 22, and controls the rotation of the motor 23 in synchronism with the clock signal from the PLL circuit 31 to keep the linear velocity of the disk 22 constant.
When a seek is performed by the pickup 25 to jump from the present track of the disk 22 to a destination track thereof, the CPU 52 controls the pickup servo unit 35 so that the pickup 25 can reach the destination track of the disk 22. In the case of the conventional apparatus 51, after the pickup 25 reaches the destination track, the CLV servo control procedure is started to control the rotation of the disk motor 23 through the disk servo unit 53 in response to the data signal read from the destination track of the disk 22.
To control the track jump of the pickup 25 to the destination track, the disk 22 is always irradiated with the laser beam from the pickup 25, and the pickup 25 is moved in accordance with track address information output from the track address detecting unit 33 during the track jump of the pickup 25.
Alternatively, a distance between the present track and the destination track is calculated based on a difference between the present track address and the destination track address, and the track jump of the pickup 25 is controlled in accordance with the calculated distance.
FIG. 4 shows another conventional optical disk apparatus 61. In FIG. 4, parts of the optical disk apparatus 61 which are the same as corresponding parts of the optical disk apparatus 51 in FIG. 3 are designated by the same reference numerals, and a description thereof will be omitted.
The conventional optical disk apparatus 61, as shown in FIG. 4, includes a disk servo unit 64 and a motor speed sensor 65 in addition to the elements of the optical disk apparatus 51 shown in FIG. 3. The disk servo unit 64 is provided separately from the disk servo unit 36 which performs the above CLV servo control procedure. In this optical disk apparatus 61, the motor speed sensor 65 supplies a signal indicating a rotating speed of the disk motor 23 to the disk servo unit 64. The disk servo unit 64 controls the rotating speed of the disk motor 23 in accordance with the signal from the motor speed sensor 65 through the motor drive unit 24 to a predetermined rotating speed. The predetermined rotating speed is defined by a target velocity signal supplied from a CPU 62 as an angular velocity at a destination track of the rotating disk 22. This is performed by the disk servo unit 64 independently of the CLV servo control procedure performed by the disk servo unit 36.
When a seek is performed by the pickup 25 to jump from the present track of the disk 22 to the destination track thereof, the CPU 62 controls the rotation of the disk motor 23 through the disk servo unit 64, so that the rotating speed of the disk motor 23 is changed from an angular velocity at the present track of the disk 22 to an angular velocity at the destination track of the disk 22.
The conventional optical disk apparatus 61 includes a switch S11 with a set of terminals "A", "B" and "c". An input of the motor drive unit 24 is connected to the terminal "c" of the switch S11. An cutput of the disk servo unit 36 is connected to the terminal "a" of the switch S11. An output of the disk servo unit 64 is connected to the terminal "b" of the switch S11.
The disk servo unit 36 supplies a servo signal to the terminal "a" of the switch S11 in synchronism with the clock signal from the PLL circuit 31. The motor drive unit 24 amplifies a servo signal from the terminal "c" of the switch S11, and supplies the servo signal to the disk motor 23 to control the rotation of the disk motor 23. The servo signal is sent from one of the input terminals "a" and "b" of the switch S11 to the motor drive unit 24 depending on which the output terminal "c" of the switch S11 is connected to either the input terminal "a" or the input terminal "b".
The disk servo unit 64 generates a servo signal by using the speed signal from the motor speed sensor 65, and supplies the servo signal to the terminal "b" of the switch S11. When this servo signal is supplied to the disk motor 23 through the motor drive unit 24, the rotation of the disk motor 23 is controlled so that the rotating speed of the disk motor 23 accords with the predetermined rotating speed defined by the target velocity signal from the CPU 62.
When data is read from or written onto the disk 22 by using the pickup 25, the terminal "c" of the switch S11 is connected to the terminal "a" thereof in accordance with a switch signal supplied from the CPU 62. Thus, the servo signal from the disk servo unit 36 is supplied to the disk motor 23 through the motor drive unit 24, so that the CLV servo control procedure is carried out.
When a seek is performed by the pickup 25 to jump from the present track of the disk 22 to the destination track thereof, the terminal "c" of the switch S11 is connected to the terminal "b" thereof in accordance with a switch signal supplied from the CPU 62. The CPU 62 supplies, at the same time, a seek start signal to the pickup servo unit 35 to start a seek operation of the pickup 25. At this Lime, the servo signal from the disk servo unit 64 is supplied to the disk motor 23 through the motor drive unit 24. Therefore, even when the seek is performed by the pickup 25, the rotating speed of the disk motor 23 can be controlled to reach the angular velocity at the destination track of the disk 22, at the same time as the pickup 25 reaches the destination track of the disk 22.
After the pickup 25 reaches the destination track of the disk 22 and the rotating speed of the disk motor 23 reaches the angular velocity at the destination track, the terminal "c" of the switch S11 is connected to the terminal "a" thereof in accordance with the switch signal supplied from the CPU 62. Thus, the data recording or data reproduction of the disk 22 is carried out by using the pickup 25 while the CLV servo control procedure is performed.
In the conventional apparatus 51 in FIG. 3, after the pickup 25 reaches the destination track, the CLV servo control procedure is started to control the rotation of the disk motor 23 in response to the data signal read from the destination track of the disk 22. However, while a seek is performed by the pickup 25, the CLV servo control procedure is not started. The time needed for performing the seek and the time needed for completing the CLV servo control procedure are necessary to complete the data recording or data reproduction. Therefore, it is difficult for the optical disk apparatus 51 to realize a high-speed data access to the disk 22.
In the conventional apparatus 61 in FIG. 4, it is necessary to additionally provide the disk servo unit 64 and the motor speed sensor 65, in order to start the CLV servo control procedure while the seek is performed. Even if the speed of the data access to the optical disk is increased, the cost of manufacture of the optical disk apparatus is considerably raised.